Production of metal electrodeposits



United States Patent F 2,905,602 T PRODUCTION OF MET L ELECTRODEPOSITS Alfred Kirstahler, Dusseldorf, and Wolf-Dieter Willmund and Weunemar Strauss, Dusseldorf-Holthausen, Germany, assignors to Dehydag, Deutsche Hydrierwerke G.m.b.H., Dusseldorf, Germany, a corporation of Germany No Drawing. Application November 2, 1955 7 Serial No. 544,586 7 I Claims priority, application Germany November '5, 1954' 7 Claims. (Cl. .204-46) This invention relates to a process for the production of bright metal electrodeposits, and more particularly to electroplating solutions having quaternary ammonium compounds dissolved therein which eliminate the adverse effects of impurities in such solutionsuponthe brightness of the electrodeposits producedtherefrom.

It is well known in the electroplating art that the brightening elfect of brightners added to electroplating 1dwthylammo'ethylchlondeiz solutions is impaired by certain inorganic impurities con tained in such solutions. Impurities which usually have such an impairing effect upon metal electrodeposits are those substances WhlCh cause the hardness of water and y a m impurities which occur in technical grade metal salts employed to prepare electroplatingbaths, particularly in inorganic copper salts used to compound acid copperplating baths. v

The obvious solution to this problem would be to employ distilled water and chemically pure metal salts in the preparation of electroplating bathsintended to be modified with brighteners. the use of such chemically pure components would not only be very impractical, but would also render the cost of electroplating objects so high as to make bright plated articles too costly. t

It is an object of the present invention to provide a method of electroplating objects in platingbaths con-. taining brightening agents, whereby bright metal elec- 9 N-(3-chloro-2-oxy propyl) morpholine However, it is evident that with the present invention.

allowed to stand for extended periods of time, or are slightly heated. In either case, the transformation 'will take place when the tertiary amines are kept for some time or warmed as such or in solution respectively. According to Rothste'in and Binovic, Comptes Rendus, 236, pp. 1050-1052 (1953), for example the transformation of N,N-diethylamino-3-chloro-propanol-2 is said to take place as follows: 5

The quaternary ammonium compounds thus formed need not be isolated or specially purified prior to their use as additives for electroplatin g ba'ths in accordance Specific examples of halogenated tertiary amines which may be transformed into quaternary ammonium compounds suitable for use as electroplating bath additives according to our invention are the following:

l-dioxyethylamino-ethylchloride-2 l-diethylamino-3-chloropropano1-2 1-dioxyethylamino-3-chloropropanol-2 N-( 2-chloroethyl -N-ethyl-aniline N- 3 -chloro-2-oxy-propyl) -N-methyl'-cyclohexylamine N,N-dicyclohexyl-N-2-chloroethyl-amine N-2-chloroethyl-piperidine Bis-(2-bromoethyl)-benzylamine, and the like.

} gm./liter of bath, preferably fro'm"2 to 8 gm./liter of trodeposits are produced despite the presence of interfering impurities in the electroplating bath.

Another object of this invention is to provide additives for electroplating baths containing brighteners, which Will render impurities present in the bath impotent as interfering substances in the production of bright electrodeposits.

Other objects and advantages of our invention will become apparent as the description thereof proceeds.

We have found that the interfering effects of impurities in electroplating baths containing brighteners can be readily eliminated by adding to such electroplating baths quaternary ammonium compounds which are formed by internal rearrangement of the molecular structure of halogen-substituted tertiary amines having the general formula bath. The particular "amount required varies from one specific quaternary ammonium compound to the other, and also depends upon the natureof the brightening agent employed as well as upon the type and amount of impurities present in'the bath.. 1 1;

In general, objects are electroplated in a bath modified in accordance with our invention at temperatures ranging from 30 to 60 C. and at current densities between 0.5 and 15 amp./dm.

Electroplating baths containing brighteningagents and modified in the above manner in accordance with our. invention will produce bright and lustrous electrodeposits over the entire effective range of current densities, de spite the presence of impurities of the above-described nature in the bath. Moreover, the quaternary am'-' monium additives according to our invention have the further advantage that they increase the ductility of the electrodeposits produced from baths modified therewith.

The quaternary ammonium compounds are eifective in the manner described in all those electroplating baths which contain magnesium and calcium ions introduced by the use of hard tap water, and ferric ions introduced by the use of metal salts of technical purity in the prep- 'aration of the electroplating solution. We havefound, however, that they do not act as water-softening agents in the usual sense, and that they can not be replaced by the typical Water-softening agents, such as sequestering agents and detergents. Nevertheless, these quaternary ammonia um additives are capable of completely eliminating "the adverse effects of the above-described impurities upon the brightness of electrodeposits produced from baths containing such impurities and brighteners.

Although the exact theoretical reason for the beneficial action of these quaternary ammonium compounds is not fully understood, it is believed that their elfect comes into' play at the surface .of the metal object being electroplated;

Patented Sept. 22, 1959v which is indicated by the high concentrations in which 7 1) a 0,115 on,

The employment of the quaternary ammonium compounds .in the manner above set forth does not necessitate any changes in the conditions under which objects are usually electroplated in metalisalt baths, particularly with respect to temperatures and current densities. The quaternary ammonium additives are soluble in acid metal salt solutions, particularly in electroplating baths made from copper salts, and they are not decomposed by the action of'heat or electric current during the plating process.

The additives described above can be successfully employed to modify all types of electroplating baths in which the presence of impurities of the type mentioned previously adversely affects the qualities of electrodeposits produced therefrom. Thus, the quaternary ammonium additives may be used in electroplating baths for electrodepositing zinc, nickel, chromium, precious metals, .and particularly copper.

The following example will further illustrate our invention and enable others .skilledin the art to understand it more completely. Itis understood, however, we do not intendto limit the invention to this example.

Example 0.75 gm./liter N,N-dipropyl-dithiocarbamic acid-n butylester-w-sodium sulfonate was added as brightening agent to an acid copper plating bath prepared with distilled water, 200 gmJliter crystalline chemically pure copper sulfate and 60 gm/liter chemically puresulfuric acid.

Iron objects were then electroplated in this bath at a current density between 0.5 and 8 amp/dmfi. The copper electrodeposits produced thereby were bright and lustrous.

As a comparison, other iron objects were electroplated under the same conditions in a bath composed of the same quantities of water, copper sulfate and brightening agent as above, except that the water was hard tap water and the copper sulfate was technically pure instead of chemicallyv pure. The copper .electrodeposits produced thereby were not nearly as bright and lustrous as those produced from thebath composed of distilled water and chemically pure copper sulfate.

Thereafter, 2.5 gm./ liter .of the quaternary ammonium compound formed by internal rearrangement of 3-diethylamino-lbhloropropanol-2 to this electroplating bath are added to eliminate the. adverse efiects of the inorganic impurities introduced by the tap water and the technical grade copper sulfate. Iron objects electroplated in this modified bath were provided with very bright and exceptionally ductile copper electroplate.

The same advantageous results were obtained by sub stituting for the quaternary ammonium compound described above the indicated quantities of the following quaternary ammonium compounds:

Amount of quaternary ammonium Quaternary ammonium compound compound added to both, gmJliter CEOH Cl 4-6 nootm on,

CHFCHI CH3 [0%, \i on.on]or 1-6 CEC: C l

CHI-CH} CH1 [o ri on.on]or 2 CHr-Cz C 1 Similarly, the quaternary ammonium additives may be used in conjunction with other brightening agents whose brightening power is adversely affected by the presence of impurities in the electroplating bath, such as N,N-diethyldithiocarbamic-acid-n-propylester-w-sodium sulfonate and 0 the like.

While we have illustrated our invention by certain specific embodiments, it will be obvious to persons skilled in the art that various changes and modifications may be made therein without departing from the spirit of the present invention or the scope of the appended claims.

We claim:

1. In a process of producing bright metal electrodeposits of metals selected from the group consisting of copper, Zinc, nickel, chromium and precious metals from acidic electroplating baths containing impurities found in hard water and in technical grade metal salts, and containing a brightening agent whose brightening power is adversely affected by the presence of such impurities, the step which comprises adding to such electroplating baths 0.01 to 20 gm. per liter of a quaternary ammonium compound having the general structural formula formed by the internal rearrangement of tertiary amines, free from carboxyl groups, having the general structural formula wherein G is a halogen atom, R is selected from the group consisting of lower alkylene and monohydroxy lower alkylene, and R and R are selected from the group consisting of lower alkyl, monohydroxy lower alkyl, phenyl, cyclohexy'l and a heterocyclic radical, which includes the nitrogen atom and the R and R groups, selected from the group consisting of morpholino and piperidino radicals, and R represents the internally rearranged R radical.

2. In a process of producing bright metal electrodeposits of metals selected from the group consisting of copper, zinc, nickel, chromium and precious metals from acidic electroplating baths containing impurities found in hard water and in technical grade metal salts, and containing a brightening agent whose brightening power is adversely aifected by the presence of such impurities, the step which comprises adding to such electroplating baths 0.01 to 20 gm. per liter of a quaternary ammonium compound having the general structural formula formed by the internal rearrangement of tertiary amines, free from carboxyl groups, having the general structural formula R2 wherein G is a halogen atom, R is selected from the group consisting of lower alkylene and monohydroxy lower alkylene, and R and R together with the N atom represent a heterocyclic radical selected from the group consisting of morpholino and piperidino radicals, and

R represents the internally rearranged R radical.

3. In a process of producing bright metal electrodeposits of metals selected from the group consisting of copper, zinc, nickel, chromium and precious metals from acidic electroplating baths containing impurities found in hard water and in technical grade metal salts, and containing a brightening agent whose brightening power is adversely afiected by the presence of such impurities, the step which comprises adding to such electroplating baths 0.01 to 20 gm. per liter of a quaternary ammonium compound having the structural formula formed by the internal rearrangement of tertiary amines, free from carboxyl groups, having the general structural formula 1 zinc, nickel, chromium and precious metals, from acidic electroplating baths containing impurities found in hard water and in technical grade metal salts, and containing a brightening agent whose brightening power is adversely affected by the presence of such impurities, the step which comprises adding to said baths 4 to 6 gm./liter of the quaternary ammonium compound having the general structural formula:

BIO-CHr-C'Ha CH2 I: N\ /CHOH CF HO-CHz-Oz CH2 formed by internal rearrangement of l-dioxyethylamino- 3-chloropropanol-2, whereby said impurities are prevented from interfering with the production of bright metal deposits.

5. In a process of producing bright copper electrodeposits from acidic copper electroplating baths containing impurities found in hard water and in technical grade copper salts, and containing a brightening agent whose brightening power is adversely affected by the presence of such impurities, the step which comprises adding to said baths 1 to 6 gm./liter of the quaternary ammonium compound having the general structural formula:

formed by internal rearrangement of N-3-chlo-ro-propanol- Z-piperidine, whereby said impurities are prevented from interfering with the production of bright copper deposits.

6. In a process of producing bright copper electrodeposits from acidic copper electroplating baths containing impurities found in hard water and in technical grade copper salts, and containing a brightening agent whose brightening power is adversely affected by the presence of such impurities, the step of adding to said baths 2 gm./ liter of the quaternary ammonium compound having the general structural formula:

formed by internal rearrangement of N-(3-chloro-2-oxypropyl)-morpholine, whereby said impurities are prevented from interfering with the production of bright copper deposits.

7. In a process of producing bright metal electrodeposits of metals selected from the group consisting of copper, zinc, nickel, chromium and precious metals, from acidic electroplating baths containing said metals wherein said baths contain impurities found in hard water and in technical grade metal salts, and a brightening agent whose brightening power is adversely affected by the presence of such impurities, the steps which comprise adding to said baths 2 to 8 gm. per liter of the quaternary ammonium compound having the general structural formula:

from interfering with the production of bright deposits of said metals.

References Cited in the file of this patent UNITED STATES PATENTS Pierce Dec. 22, 1953 Brown et a1 Apr. 26, 1955 

1. IN A PROCESS OF PRODUCING BRIGHT METAL ELECTRODEPOSITS OF METALS SELECTED FROM THE GROUP CONSISTING OF COPPER, ZINC, NICKEL, CHROMIUM AND PRECIOUS METALS FROM ACIDIC ELECTROPLATING BATHS CONTAINING IMPURITIES FOUND IN HARD WATER AND IN TECHNICAL GRADEMETAL SALTS, AND CONTAINING A BRIGHTENING AGENT WHOSE BRIGHTENING POWER IS ADVERSELY AFFECTED BY THE PRESENCE OF SUCH IMPURITIES, THE STEP WHICH COMPRISES ADDING TO SUCH ELECTROPLATING BATHS 0.001 TO 20GM. PER LITER OF A QUATERNARY AMMONIUM COMPOUND HAVING THE GENERAL STRUCTURAL FORMULA 